The invention concerns a free-wheel clutch having a shaft, a hub and clamping elements which are arranged between these and can be moved between a rest position, in which the shaft and the hub can be rotated freely with respect to each other, and a locked position, in which said clamping elements produce a frictional connection between shaft and hub in a first relative direction of rotation.
Frictional-connection free-wheel clutches constitute directionally operated clutches which can operate with radial or axial transmission of force. A distinction is drawn between free wheels having cylindrical clamping bodies, which are accommodated between a cylindrical clamping track and one provided with clamping faces and which can be formed on the shaft or the hub, and free wheels having clamping bodies which are arranged between cylindrical clamping tracks and, because of their geometry, can be clamped between these tracks in a specific relative direction of rotation. In order to ensure reliable, immediate driving in the locked direction, free wheels are most often provided with springing for the clamping bodies, which preloads the latter against the frictional face.
Free-wheel clutches of this type are used, inter alia, as roll-back stops, as overrun clutches in two-motor drives and in bicycle hubs.
In some applications, however, it is necessary that the locking action or the free-wheeling action is not exclusively dependent on the direction of rotation, but primarily on which of the parts rotates. Thus, in the case of coupling up an auxiliary drive, for example, it may be desirable for the latter in principle to be completely decoupled from the main drive and for a frictional connection in both directions of rotation to be possible only after said auxiliary drive has been engaged. A return into the free-wheeling position is to occur after the auxiliary drive has been switched off.
Applications of this type may certainly be implemented with the aid of two overrun clutches having opposed free-wheeling or locking directions, which are used alternately depending on the direction of rotation. However, external operation is necessary for this, which requires a high outlay and, for example in the case of directions of rotation which change rapidly and often, makes it necessary to use an electromagnetic clutch, which gives rise to considerable costs, is accompanied by switching noises and has a not inconsiderable energy consumption.